Cast steel



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Albert Paul Gagnebin, Fair Haven, N. 1., assignor to The International Nickel Company, Inc., New York, N. Y., a corporation of Delaware Nb Application June 1s, m, Serial 27 Claims. The present invention relates to a method of producing steel c an improved combination of properties, and more particularly to a method of consistently producing ilne grained cast steels ing good ductility combined with soundness of metal on an industrial scale inapractical manner;

It is well known that in the industrial production of cast steels of similar composition and heat treatment, castings were often defective because of excessive porosity and/or because of low ductility. Heats of similar compositionsometimeis- I yielded cast steel which low ductility when solid (and properly heat treated), while at other times the metal w: good ductility but tended to be unsound. This erratic production of cast steels resulted in products which were sometimes defective and sometimes satisfactory, but which could not be consistently duplicated. The production of good steel castings was an art reabovementioned shortcomings and which were characterized by freedom from porosity combined with good ductility. The properties of the resulting castings appeared to be influenced by numerous variables, including the type of charge used, thetype of furnace used,.the'amount of boil, the i'umaceconditions, the slag, the amount and kind of deoxidants used, and many others which those skilled in the art could not control to consistently produce castings which were sound and good ductility and other satisfactory properties required by the trade.

'; In view of the erratic production of cast steels and in view of frequent production of castings with low ductility ,an'd/or excessive porosity, those skilled in the art were aware of the vexatious nature of the problem facing the art and were diligently attempting to solve it. Numerous attempts and proposals have been made to solve the problem. Many deoxidizers and degasiilers have been proposed for the production of sound metal, but it has been found in actual practice that the product had a tendency to be low in 1 ductility, unsuitable for commercial practical ap- Metallurgical Engineers, 1932. vol. 100, page 154.

In Canada May 18, 1940 were attempting to solve the problem, but found from their tests that steels deoxidized with aluminum low ductility, and were not always free rom porosity. When aluminum was 5 used 'it was observed that there was a change in .inclusions accompanied with a decrease in duotility, Principally in the reduction of area. Occasionally the addition of aluminum did not affect the ductility, while on the other hand, the erratic l0 behavior of the methods of producing steel would be further evidenced by steels which possessed low ductility even when not treated with aluminum. Other investigators have also published results showing that deoxidation with aluminum causes a decreased elongation and reduction of 1 area of the cast steel.

aluminum have been described by McCrae et al. in their article in the U. S. Department of Commerce, Bureau of Standards Journal of Research,

go vol. 5, 1930, page 1123. Steels deoxidized with .quiring. considerable skill and good fortune in order to obtain metal which did not the amount of oxygen was required for sound, ductile steel, but it has been very dliilcult to control and very diiilcult to obtain the proper amount of oxygen in cast steel to yield a product free from porosity combined with good ductility, etc. Prior procedures in steel practice did not give assurance of the production of high quality steels which were consistently free from porosity combined with high physical properties,

ductility. As pointed out hereinbeford, the use of'strong deo xidizers promoted low ductility but they we're sometimes considered necessary to secure freedom from subsurface porosity. L The biggest obstacle to the production of good quality 40 cast steel, deoxidized in the regular manner with l manganese and silicon. was the necessity for very accurate control of the iron oxide content of the molten steel. A high oxygen or oxide content often resulted in porosity, and while 'a low .0mm or oxide content promoted soundnessv it also promoted low ductility. Furthermore, no sumciently rapid method for measuring the oxide content ofa molten steel bath was known. Thus,

'the assurance of soundness by the useof'strong 0 deoxidisers suehfas aluminum.ands'ilicon -pro- The aforesaid effects ofmoted low ductility and the use of manganese and silicon deoxidation did not assure the production of cast steel which was consistently -sound and ductile in commercial practice. Although many attempts were made to remedy the aforementioned shortcoming, none as far as I am aware, was entirely successful when put in commercial operation on an industrial scale in'consistently producing satisfactory results and could be carried into practical and economic industrial scale operation.

I have discovered a method of producing steel free from the disadvantages and defectsnoted hereinabove which consistently makes sound steel castings having improved physical properties, e. g., high ductility, etc., and devoid of porosity and which is capable of being carried, into practice satisfactorily and economically when operated on an industrial scale for the manufacture of commercial steel castings. I have also discovered that selenium and/or tellurium not only desensitize the effect of sulfur but also produce pronounced grain refinement in steels which in the absence thereof would be coarse grained. Both elements are weak deoxidizers so that it is possible to produce a partially killed fine grained steel whereas the usual grain refining elements, such as aluminum, titanium, vanadium and the like, have always been strong reducing elements or strong carbide formers or both. The term fine grained steel as used herein is in accordance with general metallurgical usage and means that the grain size is small after cooling through the transformation temperature, as in normalizing; other-types of tests such as the McQuaid-Ehn test similarly show the grain refining efifect of selenium and/or tellurium. The terms fdesensltizing or sulfur-desensitizing agent as used herein refers to the ability of selenium and of tellurium to. counteract or otherwise decrease the detrimental-effect of sulfur upon ductility, particularly in low oxygen or oxide melts. The terms also refer to the ability of selenium and of tellurium to cause the sulfur,

or sulfides, to 'occur globularly and randomly distributed rather than in the chain-like, intergranular occurrence which is associated with low ductility in cast steels.

It is an object of the present invention to provide a method of producing cast steel which is simple, practical and economical and which is capable of being operated consistently and successfully on an industrial scale to produce satisfactory and commercially acceptable products.

It is another object of the present invention to provide a method of manufacturing steel whereby castings can be consistently produced not only free vfrom porosity but also with high physical properties, especially high ductility particularly with respect to reduction of area.

It is a further object of the invention to provide a method of producing steel which con-- sistently yields fine grained cast steels substantially free from porosity and chain-like intergranular distribution of inclusions, particularly chain-like sulfide inclusions, and which consistently produces sound cast steels wherein the sulfide inclusions are globular and randomly distributed.

The invention also provides a melting process for producing cast steels which involves a novel combination of .operations and which permits the use of strong deoxidizers to thoroughly kill the steel; which produces random distribut on of inclusions, particularly sulfides, and which consistently makes a sound cast steel having,

It is further within-the contemplation of the' present invention to provide fine grained cast steels characterized by'freedom from blowholes combined with high ductility and containing small controlled amounts of selenium and/or tellurium.

The invention also contemplates fine grained cast steels containing fractional percentages of a strong deoxidizer, generally aluminum and/or silicon,' and small controlled amounts of selenium and/or tellurium to eliminate the adverse effect of aluminum and/or silicon upon the sulfide distribution which would occasion a serious loss of ductility. 1

The invention also contemplates fine grained cast steels containing fractional percentages of a strong deoxidizer, such as aluminum and/or vanadium and/or silicon, small controlled amounts of selenium and/or tellurium, and small amounts of calcium and/or other alkaline earth metal and characterized by soundness of metal combined with high physical properties, especially high ductility.

The invention further contemplates a method of incorporating .small controlled amounts of selenium and/or tellurium and calcium into the molten steel which will give predictable and controlled recoveries of selenium and/or tellurium and/or calcium in the final product.

The invention also provides a novel addition compound containing seleniumand/or tellurium and calcium characterized by a fast rate of reaction and capable of introducing predictable, controlled amounts of calcium and selenium and/or tellurium in the molten steel.

Other objects and advantages of the invention will become apparent to those skilled in the art from the following description.

In general, the present invention involves a novel combination of operations which comprises establishing or producing a molten mass of steel or ferrous alloy in the customary manner but without regard to the accurate oxygen or oxide control which has been required heretofore, treating said molten mass of steel, for example, in the ladle, with about 0.05% to about 0 .6% of at least one sulfur-desensitizing agent from the group consisting of selenium and tellurium, and casting the molten steel thus treated whereby cast steels are consistently produced which posseas improved ductility regardless of the oxide content of the steel. I have discovered that small amounts of selenium and tellurium have a powerfui desensitizing eflect on the sulfur present in the steel and promote high ductility in the final Heretofore it was believed that I Table IV. Composition: 1.5% Ni; 1.2% Si; 1% Mn; 0.2% C; 0.04% S Steel No. Treatment of molten metal Regular Si-Mn deoxidation. Regular Si-Mn deoxidation, then 0.05% Ga, and

0.03% Se added.

Table V Composition: 1.75% Ni; 0.25% Mo; 0.85% Mn; 0.35% Si; 0.28% C;

Steel No. Treatment of molten metal Regular Si-Mn deoxidation. Regular Si-Mn deoxidation, then 0.03% Se, and

I Y. P.-yield point in thousand pounds per square inch.

.--tensile strength in thousand pounds per square inch. ercent El.=percent elongation. Percent R. A. -percent reduction in area. Impact-charpy impact in foot-pounds (V notch).

Melts which vary considerably in iron oxide content and which would difier widely in properties and soundness if deoxidized in the normal way with silicon and manganese will be uniform- 1y sound, ductile and fine-grained when finished with selenium and/or tellurium in conjunction with a calcium-containing intensifying agent.

Low ductility is consistently associated with intergranular, chain-like sulfides while good ductility is obtained when the sulfides are globular and randomly dispersed. The type of sulfide inclusion is normally related to the oxygen or iron oxide content of the steel, intergranular sulfides being obtained with low oxygen and iron oxide contents and randomly distributed sulfides being characteristic of high oxygen and iron oxide contents. A characteristic and consistent relationship exists between low ductility and intergranular sulfides. Intergranular sulfide condition may occur with any melting process, including the acid electric, basic electric and basic open hearth processes. oxide content has been required for good'fiuidity and ductilityqbut unfortunately this frequently led to excessive porosity in the casting. Porosity may develop because of 'insufiicient deoxidation prlorto casting. Low ductility will result because of the production of chain sulfides due to the absence of sufi'lcient ongen in the melt promoted steels but so lowers the oxygen content as to cause the sulfur to precipitate intergranularly and rethe like with none as low ductility.

be obtained in the product. Thus,'where about- 45.

A. relatively high oxygen or sults in low ductility when cast. Its normal use is precluded in steels, particularly alloy steels, with high ductility requirements. In some instances, small amounts of aluminum are even more detrimental than larger amounts. Thus, it has been observed that additions of about 0.02% aluminum appears to lower the ductility of cast steels to lower levels than do smaller or larger amounts. The present invention enables the art to use strong deoxidizers such as aluminum and of its detrimental effects, such Silicon, a fairly strong deoxidizer, also promotes low ductility and intergranular sulfides when used in amounts suflicient to completely deoxidize the steel and assure sound metal when cast. I have found that manganese appears to be an undesirable desulfurizer under reducing conditions as it forms sulfides that appear in the grain boundaries.

Selenium and/or tellurium, either alone or preferably in conjunction with an agent such as calcium, are able to nullify the detrimental effect of sulfur,-or sulfides, apparently by coalescing the sulfides, particularly in a low oxygen or oxide steel, to produce globular randomly dispersed sulfides and high ductility in the final cast steel instead of the intergranular, chain-like sulfides and low ductility normally obtained in low oxygen or completely deoxidized steels. Selenium and tellurium ave two other useful and unexpected attributes in that they are mild deoxidizlers and that they refine the normalized and McQuaid-Ehn grain size of the steel. The average McQuaid-Ehn grain size of selenium and/or tellurium treated steels is about No. 6 to 7, although some No. 4 and No. 5 grains have been observed occasionally.- Usually, over about 50% of the selenium and/or tellurium remains in the final product, although in one instance a recovery as low as about 10% was observed. Under oer tain conditions substantially full recovery may 0.1% selenium was added to one steel, upon analysis 0.09% remained in the product. In general, the recoveries will depend upon many factors, including the state of oxidation of the molten metal, the efliciency of the method of addition, for example th form of the addition material or the thoroughness with which the matelntenslfying rial is incorporated below the surface of the molten metal, the holding time before casting, etc.

It has been found that the present invention is particularly beneficial in the treatment of steels subjected to deoxidation with a powerful deoxivdizer such as aluminum in amounts of about 0.01% to 0.25%, usually about 0.03% to 0.08%, in conjunction with the sulfur-desensitizing treatment with selenium and/or tellurium. Table VII lists several nickel-manganese steels and the .various treatments to which portions of the heats reducing conditions duringmelting, by the use of strong deoxidizers, etc. The desire for steel. It'has been noted that aluminum-killed steels to. 0.08% or more, which assures soundness in cast low ductility. Aluminum is an excellent deoxidizer, for example in amountsof 0.03 l

were subjected. Table VIII gives the properties of the resulting steels. All steels were subjected to treatment withaiuminum, a powerful deoxidizer. prior to treatment in accordance with the present invention. As pointed out hereinbefore. treatment with aluminum has been considered detrimental where high ductility was required, and small amounts of the order-of 0.02% are fre. quentiy more detrimental than larger amounts. Steels Nos. 13 to 15, 18 to 20, 23, 25 and 26 which were treated in accordancev with the present invention all showed a notable. recovery in reducselenium and/or tellurium to a steel containing sulfur would further lower its ductility. I have made the astonishing discovery that'quite the reverse is true and that the addition of selenium and/or tellurium to steel has the remarkable efexample, in the presence of small but effective,

amounts of at least one alkaline earth metal, preferably a calcium-containing intensifying agent such as elemental calcium'or calcium silicide, smaller amounts of selenium or tellurium may be used with more powerful and advantageous effect. The amount of calcium and/or other alkaline earth metal used may vary within the range of about 0.03% to about 0.6%, for example about 0.05'% to about 0.15% calcium, and

q the amount of selenium and/or tellurium used in conjunction with the calcium-containing intensifying agent may vary from a small but effective amount, or about 0.01%, up to about 0.6%, for example about 0.02% to 0.08% selenium and/or tellurium. Increasing amounts of the intensi tying agent, for example calcium, permit the use of lesser amounts of selenium and/or tellurium. Excellent results have been obtained by treating the steel with about 0.03% selenium and about 0.05% calcium. Calcium is very effective and low in cost so that it is preferably employed as the intensifying agent. Other alka ine earth elements having appropriate solubilities in iron and moderate vapor pressures such as barium and strontium may be used as alternates to calcium or in conjunction therewith but seem less appropriate principally because of their higher cost. The use of magnesium as an intensifying agent has been precluded by practical difliculties in incorporating it in the molten metal apparently due to its high vapor pressure. when I use the term intensifying agent" in referring to materials such as calcium and alkaline earth metal I refer to the property of these materials to enhance the desensitizing power of selenium and/or tellurium and to render the selenium and tellurium active in smaller amounts than when to also function as economizers.

In the absence of an intensifying agent such usual manner. The improved ductility resulting from the selium or tellurium treatment is evisaid intensifying agent isnot present and thus, 5

as calcium, at least about 0.05% of selenium and/or tellurium appears to be required in order to'obtain' appreciable beneficial effect in normal steels. In general, as the sulfur-content increases above normal values, i. e., above about 0.05%, the minimum selium and/or tellurium content required to obtain a beneficial effect should also be increased accordingly, and, p'referably, the manganese content should also be increased.

Although an equal fractional percentage of selenium appears to be slightly more effective than tellurium. the addition of about 0.1% of either or both to normal steels has produced satisfactory results in actual practice. In Tables I and II two nickel-manganese cast steels produced in accordance with the present invention are compared with a similar steel made in the denced by the higher elongation and reduction of area, particularly the latter, of steels No. 2 and No. 3 as compared to steel No. 1 finished with 0.02% aluminum in accordance with common practice.

Table I Composition: 1.5% Ni; 1.5% Mn; 0.36% Bi; 0.3% O; 0.035% 8 Steel No. -Treatment of molten metal 0. a A] added. 0.1 added. 0.1% To added.

Table II Heat treatment: normalized and drawn Mechanical properties Y. 'P.-yleld point in thousand pounds per square inch.

T. S.tensile strength in thousand pounds per square inch.

Percent 01. -percent elongation.

Percent R. A.- percent reduction in area.

In carrying the invention into practice it is preferred to use a calcium-containing intensifying agent in conjunction with selenium and/or tellurium. Smaller amounts of selenium and/or tellurium in conjunction with the intensifying agent give better results than are obtained with larger amounts of selenium and/or tellurium in the absence of the intensifying agent. Tables III, IV, V and VI give the results obtained from steels treated in the usual manner with silicon and manganese and from similar steels treated in accordance with the present invention with a calciumcontaining intensifying agent in conjunction with selenium and/or tellurium. Table III gives the treatments applied to a nickel-manganese steel, while Table IV gives a similar data for a nickelsilicon steel and Table V for a nickel-molybdenum steel. The resulting properties are given in Table VI. Steels Nos. 5, 6, 8 and 10 were treated in accordance with the present invention while steels Nos. 4, 7 and 9 were treated in the usual manner with silicon and manganese prior to cast- Table ,111

. Composition: 1.5% Ni; 1.5 Mn; 0.35% Si; 0.3% o; 0.035% s Treatment of molten metal Regular Eli-Mn deoxidation.

Regular Si-Mn deoxidation, then 0.05% Cu, and

0.037 Te added.

0.05% 6a and 0.03% as added.

Percent 4 tion in area and/or elongation, particularly the i'ormer, compared with the properties oi the steels after treatment with aluminum alone (steels 11, 16, 21 and 24) or aluminum and insuiiicient amounts of selenium (steels 12, 17 and 22). Itwill be noted that steels Nos. 21 to 23 contained much more than the usual amount of sulfur round in steel and-illustrate the electiveness oi the present invention in desensitizing sul- Table VII Composition: 1.5% Ni; 1.5% Mn; 0.4% Si Percent P ge Treatmentotmolteu metal 999 999 P9999 99999 222 New seems I Percentages given are amounts added.

Table YIII Heat treatment! normalized and drawn Mechanical properties 7 Steel No.

Penent Percent m. 11...;

$ 2 $55 3. 5. one": uneenqoaq 5F; 5 85 Q9 move I See iootnote to Table VI ior key to symbol.

I is normally found in high grade cast steels.

Table IX Composition: 1.51% Ni; 1.43% Mn; 0.3% s1; 0.21% o g Treatment of molten metal Partly oxidized, then 0.06% A] added.

To added.

Same as 27, then 0.06;,

Same as 27, then 0.16 0 Te added.

0.06% Al and 0.06% Te added. 0.06 o Aland 0.1% Te ad. ed.

0.06 Aland 0. a To added. 0.00% Al and 0.3 a To added.

Table X Heat treatment: normalized and drawn Mechanical properties Steel N 0.

Percent Percent m: R. A.

2.822 2.22 ORIGIN new .2222 2.2.2 Q03: OIQIO 2. .2.: 2.2.2 -r-la-1 1 See iootnote to Table V1 for key to symbols.

It has been pointed out hereinbefore that it is preferred to use a calcium-containing intensitying agent in conjunction with the selenium and/or tellurlum treatment and that in the presence of such an agent smaller amounts of selenium and/or tellurium are as -eilfective as much larger amounts in the absence of the intenaiiying agent and in many instances the former treatment is more effective. Where the use of strong deoxidizers such as aluminum are desirable, for example, in amounts ranging from about 0.01% to about 0.25%, treatment with small amounts of selenium and/or tellurlum 1n conjunction with a calcium-containing intensifying agent such as metallic calcium or calcium silicide has proved very eiljective. Tables XI, XII,

treatment as illustrated by steels Nos. 36, 38, 40, 41 and 43. The steels set fourth in Table XIII were melted in a regular three' phase direct arc furnace.

Table XI Compofltion: 1.5% Ni; 1.5% Mn; 0.4% 81; 0.3% C; 0.006% 8 Treatment of molten metal 1 Steel No.

0.0a 0.00% A]: then-0. He, then 0.1% Ca.

i Percentages given are amounts added.

Table XII Composition: 0.8% Mn; 0.4% Si; 0.28% O; 0.135% S Steel No. Treatment oi'moiten metal 1 fi g Mow! Be I e1 o. as]: then 0.1 a then o.1%se.

I Pementues than are amounts added.

XIII and XIV show the eiiectlveness of such Table XIII Table XVI Composition: 1.27% Ni; 1.35% Mn; 0.25% Si; 0.3% C; 0.035% 8 Heat treatment: double normalized and drawn Steel No. Treatment of molten metal 5 Mechanical propcrms Steel No. 0257 A] Y P T S Pclracent Plclrcgnt o 0.025% Al, then 0.05% Ga and 0.03% Se.

90. 12. s 17. 4 l Percentages given are amounts added. 36.0 25.0 39. 1 80. Z 23. 7 40. 0 Ta le IV 86. 5 25. 0 43. 7

72. l 4. 5 7. 4 Heat treatment: normalized and drawn 87. 2 22.0 30. 0

l See footnote to Table VI for key to symbols.

When cast steels which possess good properties in light sections are poured into heavier sections, the properties are frequently detrlmentally afiected. The property most adversely affected appears to be the ductility. There is reason to believe that this may be attributed, at least in part, to poor sulfide distribution. Treatment of steels in accordance with the present invention has beenfound to have beneficial effect upon. the ductility oi"- steels cast in heavy sections. Tables XV and XVI give various treatments and the resulting properties of a nickel-manganese steel cast into heavy sections 3 inches by 5 inches by 5.5 inches. The improvement in ductility imparted by treatment with selenium or tellurium, as illustrated by steels 15, 46, 47 and i9, is very pronounced. The marked, beneficial effect of the selenium and/or tellurium treatment on strongly deoxidized steels is shown by comparing the properites of steel No. 48 with steel No. 49. Steel No. 48 is a nickel-manganese steel deoxidized with both silicon and manganese and with aluminum, whereas steel No. 49 is another heat oi the same composition treated with silicon, manganese and aluminum plus further treatment with selenium in accordance with the present invention. The recovery in reduction in area and elongation in the heavy section after the selenium treatment is very pronounced.

Table XV Composition: 1.5% Ni; 1.5% Mn; 0.3% C; 0.35% Si; 0.035% S Steel No. Treatment of molten metal 1 Regular Si-Mn deoxidation, then 0.06% Al. Regu ylarS Si-Mn deoxldation, then 0.06% Al and 1 Percentages given are amounts added. 7

1 See footnote to Table VI for key to symbols.

I have discovered that increased impact values at low temperatures can be secured by applying the present invention to aluminum-containing steels, for example, 'a steel containing about 0.08% aluminum, and have also made the important discovery that the present invention unexpectedly produces high impact values even in steels free from aluminum. Table XVII gives the low temperature shock resistance at various temperatures of a 3.5% nickel steel containing about 0.1% carbon, about 0.65% manganese, about 0.35% silicon, normal sulfur and small amounts of treating agents. The steels were subjected to a heat treatment comprising air-cooling from 1750 F., then oil-quenching from 1525 F. and. air-cooling from 1200 F.

Table XVII D Impact (keyhole notch) 3 Treatment g g .05 C8, .03 Se 67. 3 30. 5 31. 5 2 .OBSAI, .05 Cu; .03 63. 3 38 29. 5 20. 3

.1 Se G2. 8 34. 8 27 22. 3

Impact-Charley impact, foot-pounds (average of 2 values).

R. T.=-at room temperature.

It will be observed that the present invention provides a method of treating cast steels, including plain carbon steel, alloy steels, and other iron basev alloys subject to the difficulties and dlsad vantages mentioned hereinbefore. Cast steels normally contain about 0.025% to about 0.05% sulfur, but steels containing 0.07% to 0.09% sulfur have also been successfully treated, and steels containing even larger quantities as high as about 0.15% sulfur will be usefully improved. Cast steels flnishedln accordance with the present invention can tolerate larger quantities of sulfur with better ductility than steels finished with silicon and manganese. Nickel steels containing about 1.5% manganese and 0.09% sulfur (which is two or three times the normal sulfur content) had acceptable ductility after the addition of 0.05% calcium and 0.03% selenium. In general, as the sulfur content increases above about 0.06% it is preferred to increase the manganese content above normal values, for example, above about 0.65%. Increased amounts of sele nlumor tellurium and/or calcium or other intensifying agent also tend to compensate for increased sulfur contents. The addition of aluminum appears to lower the quantity of sulfur that can be tolerated. Should the sulfur exceed the upper limit of the range normally found in steel, 1. e., about 0.05% a larger amount of sulfur-desensitlzing agent'and/or the intensifying agent should be added than is normally added, as will be apparent to those skilled in the art. Steel baths containing below about 0.015% or 0.02% sulfur which can only be achieved with greater difliculty and at much higher cost, apparently do not contain sufllcient sulfur to markedly affect the ductility and such steels are fairly successfully treated by prior art methods, e. g., killing with aluminum, a treatment which cannot consistently produce satisfactory results with higher sulfur contents, although the present invention may also housed in treating such low sulfur steels. Cast steels containing less than about 0.015% sulfur are comparatively rare and are not usually met with in ordinary cast steel practice. When I refer herein to "small but detrimental" amounts of sulfur I include within the scope of the expression amounts of sulfur which when present in well killed steel castings lower the ductility as compared to a casting of similar composition but containing less sulfur, or amounts which tend to pro-- duce intergranular sulfides, or amounts which when present in a steel casting will possess higher ductility when treated in' accordance with the present invention than when not so treated or not otherwise specially treated to decrease the deleterious effect of the sulfur.

The cast steels contemplated by the present invention may contain various amounts of earbon, say about 0.05% to about 0.75% or even up to about 1.7%, frequently about 0.1% to about 0.6%, and usually about 0.25% to about 0.45%, and may 7 contain various amounts of alloying elements such as nickel, chromium, manganese, silicon, molybdenum, vanadium, copper, and other strengthening .elements, say from an effective percentage or 0.01% to about 7% or 9%, or more, and I desire that the amounts of these strengthening elements shall fall within the practical range within which the sulfide distribution has an important influence upon ductility. Usually the caststeels will contain incidental elements and impurities commonly present as a result of good steel making practice, for example, phosphorus, manganese, silicon, etc., as those skilled in the art will readily understand. The iron content normally will exceed about 90 The present invention is applicable to a wide range of plain carbon cast steels and alloy cast steels containing the usual incidental elements, deoxidizing elements, and impurities. It has been.

found that certain special deoxidizers such as titanium or apparently zirconium impair response to the'present invention and are preferably avoided or used very sparing In addition tothe above-mentioned elements normally found in steels, the cast steels produced in accordance with the present invention contain, in the final product, about 0.02% to about 0.5% of selenium and/or tellurium, preferably about 0.05% to about 0.1%. When a calciumcontaining intensifying agent is used in conjunction with selenium and/or tellurium, the percentage of the latter in the final product may be about 0.004% to about 0.5%, often about 0.01% to 0.05%, and the calcium (and/or other alkaline earth metals) may be present in amounts ranging from a small but effective amount, for example about 0.001% or 0.002%, up to the amount resulting from adding about 0.6%, for example, about 0.016% residual calcium usually about 0.003% to about 0.005% of calcium will remain in the product. As pointed outhereinbefore, the present invention is applicable to aluminumtreated steel and consequently the final product may contain from a small but effective amount, say 0.003%, up to about 0.2%. of aluminum and the like, and usually about 0.01% to about 0.05% or 0.06% aluminum, when treated with aluminum. These aluminum contents may be present in steels containing selenium and/or tellurium in the amounts indicated hereinbefore or in steels containing an intensifying agent, for example calcium, in conjunction with the selenium and/or tellurium in the amounts indicated hereinbefore and may be useful in giving a wide margin of safety against subsurface porosity.

It should be noted that calcium determinations of the order involved herein are extremely difllcult to make. Analysis by the chemical wet method involvesa lengthy procedure and many operations and may give rise to results not truly corresponding to the actual calcium contents. The values set forth herein for calcium havebeen .checked and are reproducible by the chemical wet method used for the determinations. Other methods, such as the spectographic method,

might give other results but it is to be understood that regardless of the results obtained by other methods, the values given herein are based on -manganese steels, nickel-molybdenum steels,

nickel-chromium steel, nickel-vanadium steel,

nickel-silicon steel and copper steel are given as examples;

Table XVIII Composition Steel No.

Percent Percent Percent Percent Percent 0 Ni Si Mn others .3 35 1 3. 83 35 3 l. 6 35 3 1. 27 25 28 1. 75 35 35 l. 5 35 3 l. 5 35 22 l. 5 1. 2 55 s Steels 54 and 56 to'61 were treated with about 0.02% aluminum, about 0.03% selenium and about 0.05% calcium. Steel 55 was similarly treated except that aluminum was omitted. Steel 62 was treated with about 0.1% selenium,

' no calcium or aluminum being used. The final cast steels contained small amounts of the treating agents. Steels 54 to 61 contained approximately 0.012% to 0.03% selenium, for example 0.017% and 0.023% selenium, and 0.003 to 0.005% calcium. Steels 54 and 56 to 61 also contained approximately 0.005% to 0.01% aluminum, for example 0.007% aluminum. Steel 62 contained approximately 0.08% selenium. The resulting properties of the foregoing steels after heat treatment are given in Table XIX. For comparative purposes the mechanical properties of the same steels without special treatment with selenium or calcium and selenium are also given for most of the steels and are designated by'the letter A. The steels produced in accordance with the invention are designated by the letter B.

Table XIX Mechanical properties Steel No. t

Y. P 1 'I. S. g g g Impact 1 See footnote to Table Vl-for key to symbols.

In carrying the invention into practice the calcium-containing intensifying agent is pref erabiy calcium silicide, e. e., the ordinary calcium-silicon alloys oi commerce containing about 25% to about 35% calcium. The selenium or heats, bags containing calcium silicide can be, A

throvm into the stream being tapped into a ladle in such. a manner that the bags are carried beneath the surface. it pure .or elemental seleniun be used, it should be forced into the molten metal because it volatilizes so readily. Ferro seienium is the better form for direct addition because it d ssolves readily when contact with the melt and apparently with lower loss than when added in elemental form.

In actual practice, it is preferred to use an addition compound having a special composition. The use of this special addition compound overcomes the dificulties encountered by other methods, such as the tendency of calcium to oxidize on the molten metal surface or the tendency of selenium to vaporize thus making for variable, inemcient and unpredictable recoveries in the melt. These dificulties are particularly important in large heats where it is virtually impossible to attach the constituents to rods and plunge them beneath the surface of the molten metal. Many of the steels set forth hereinbefore were treated with the special addition agent.

A special addition compound and method of addition is provided by the present'invention which successfully overcomes the difilculties of other methods and results in the incorporation of predictable, controlled amounts of the treating agents into the molten metal and produces higher ductility in treated steels than a. similar steel treated with like amounts of treating agents but not with the special addition compound. The addition compound comprises a special combination of components in powdery or other particulate form, which are essential to yield a product having the desired improved properties including a greatly increased reaction rate, 1. e., decreased reaction time. The term powder" is used herein to include material in powdery or other particulate form. It has been found that a short reaction time is necessary to give predictable and controlled recoveries in the present invention. It has been discovered that certain materials have the unexpected property of greatly accelerating the reaction rate' of calcium silicide and/or the sulfur-desensitizing agent. Suitable reaction-accelerating agents include fiuxing materials which are stable and active at molten steel temperatures and are characterized by low viscosity at these temperatures. Satisfactory reaction-accelerating agents include fluorides, for example, cryolite, calcium fluoride,

sodium fluoride, potassium fluoride, and the like. One or more reaction-accelerating agents may be used. In conjunction with the reaction-accelcrating agent, iron and/or nickel powders further increase the reaction rate, there apparently being a cooperative effect between the metallic powder and the reaction-accelerating agent. The preferred addition compound, preferably as a compacted mass, comprises, in powdery form, at least one reaction-accelerating agent, at least one metal from the group consisting of nickel and iron, at least one suliur-desensitizing agent from the group consisting of selenium and tellurium, and at least one alkaline earth metal. preferably a calcium-containing material such as calcium silicide which is a commercial alloy of calcium and silicon in varying proportions. As will be ap arent to those skilled in the art, other materials, including inert materials and minor constituents, might be present without substantially detracting from the advantages of the special combination of ingredients contemplated by the present invention.

The special addition compound provided by the present invention preferably comprises in controlled and balanced proportions about 5% to about 56% or at least one powdered reactionaccelerating agent, about to about 50% of an agent from the group consisting of iron and nickel powders, and balance, not less than about 16%, substantially all powder containing calcium at least one powdered sulfur-desensitizing agent from the group consisting of tellurium and selenium in the desired proportions, preferably in the proportions set forth hereinbefore; for

example, in the ratio of about. 5 parts of calcium to about 3 parts of selenium. A somewhat narrower and satisfactory range is about 5% to about of at least one powdered reactionaccelerating agent, about 10% to about of a powdery agent from the group consisting of iron and nickel, and the balance, preferably about 40% to about substantially all powder containing calcium and at least one powdery sulfur-desensitizing agent from the group consisting of tellurium and selenium in the desired proportions. If desired the selenium and/or tellurium may be precombined with the nickel and/or iron, for example as nickel or iron selenide or telluride. Calcium in the form of calcium silicide is ordinarily used and is preferred by the industry as a means of incorporating calcium but this form appears to present particular difliculty and the present invention is particularly adapted for the incorporation of calcium sillcide into a molten bath. Other forms of calcium and other effective alkaline earth metals may also additions maybe incorporated-into the melt in suitable manner, for example, they may be enclosed in a screen and inserted into the melt.

Preferably. the mixed powders'are slightly moistened with water or otherliquid, compressed into a convenient form and drledat about 210 F. to about 250' 1". if water be used to dampen the powder.

It has been found advantageous to should be about 100 mesh 'or'flnerand thoroughly mixed. The powdered incorporate in the mixture a small but effective amount, for example about 1% to about 2%, of an agent such as dextrine. sodium silicate, cellulose lacquer, shellac, bronzing liquid and the like to, act as a bond for the compacted mass. It is to be understood that whenI say the balance is substantially all calcium silicide and at least one sulfur-desensitizlng agent" I do not exclude small amounts of a bonding agent' and minor constituents and impurities which may be present in commercial practice or may be added for known purposes.

The addition compound has been found to be particularly advantageous where aged calcium silicide particles are used. Freshly ground calcium silicide appears-to be more reactive and ac--- "cordingly its use in the addition compound may require a decrease in the amount of reaction-acvceler'ating agent to avoid too rapid reaction rates.

Where iron or nickel alloys of selenium and/or tellurium are used instead of elemental selenium or tellurium, the iron or nickel contents of the alloy. should be considered in determining the "amount of iron or nickel powder to be incorporated in the addition compound. ,An'illu'strative example of an addition compound, preferably in compacted form, which has given satisfactory results comprises about nickel powder, about fluorspar (calcium fluoride), about 11% selenium, about 57.5% of calmain Compound N6.

It will be apparent that compounds Nos. 4 to No. 9 made in accordance with the invention, have greatly increased reaction rates over the other compounds, particularly No, 1 and No.2.

Compressed briquettes consisting entirely of calcium silicide and selenium reacted very slowly and required several minutes of stirring for solution. The addition of iron powder alone to the mixture did not appreciably increase the rate of reaction. It should be mentioned, however, that the addition of nickel powder did have a greater effect upon speeding up the reaction ratethan iron powder alone. In the presence of an agent such as calcium fluoride, etc., the addition of iron or nickel powder, or both, greatly speeded up the p reaction rate and gave excellent results as evidenced by compounds No. 4 to No. 9.- The addition compounds provided'by the invention possess improved rates of reaction and when incorporated in molten steel yield a product containcium silicide (the calcium silicide containing 32% calcium) and about 1.5% of dextrine. -A similar addition compound containing about 10% of iron powder or of ironand nickel powder will also give the addition compounds contemplated by the "present invention are necessary to stimulate the reaction of the addition compound and are an essential feature of the present addition compound. The marked improvement in the reaction time, i. e., the time required for' solution,- of addition compounds made in accordance with the present invention over other compacted mixis shown in Tables x and xxx. In these to about 3 parts selenium.

Table xx Composition CaBi (calcium silicide) and Se. j ".1"e,balanoeCaSiandBe.

g. Only, 1.6? Na SiO balance C881 and Se.

Is, 107 aFa, 1.5% Naasioi, balance CaSi and i Ni, 'NaF, balance Casi and 8e. Ni, Cal balance Casi and Be. l 0 Ni, CaFs, 1.57 dextrine, balance CaSi and i'rs, 20% can, r595 dextrine, balance ass: and

satisfactory results. The special constituents in 4 In the preferred embodiment, the' addition compound contains either iron or nickel powders or both in conjunction with a reaction-accelerating agent. However, under certain conditions where very rapid reaction rates are not'essential,

other metallic powders, for example cop'pen might be used or the metallic powders may be the calcium silicide and selenium were" 1 fihe ratio of about 5 part calcium omitted. Thus, compound-No. 3which contained no metallic powder; showed marked improvement over compounds devoid of a reaction-'-accelerat-- ing agent'as exemplified by compounds *1 and 2.

Compound No. 4 which contained the same.

amount of the reaction-accelerating agent, calcium fluoride, that was present in compounds No.

' 3 but contained iron powder had substantially twice as rapid a reaction rate as compound No. 3. Furthermore, while it is definitelyprei'erred to incorporate both calcium silicide and selenium and/or tellurium in the addition compound,- an addition compound substantially devoid of selenium and/or tellurium maybe used to some advantage where it is desired to incorporate calcium silicide into a molten bath of steel-or other alloy.

It will be appreciated that the present invention also provides a methodof treating molten steels and other alloys which comprises establishing a molten mass of steel or other alloy, in-' ,corporating in said molten'mass desired amounts of the addition compounds described hereinbefore, and casting thethus-treatedmolten mass porosity. The 'ad-.

.tainingabout whereby predictable, controlled amounts of the treating agents are incorporated in the final product.

While the invention has been described with particular reference to steel castings and products which are cast substantially in the shape or size in which they are to be ultimately used,

it is applicable to centrifugal castings, rolls and cast gear blanks and other products whose prop- .erties reflect the properties of the metal as cast.

amounts as occur in commercial practice or in amounts not adversely affecting the desired properties of the product; Such variations and modifications apparent to those skilled in the art are considered to be within the purview and scope of the appended claims.

I-claim:

1. A 'method of producing ductile cast steels free from porosity which comprises treating a molten mass of steel containing sulfur with a small but effective amount to about 0.6% of an intensifying agent comprising alkaline earth metal and a small but effective amount to about 0.6% of at least one sulfur-desensitizing agent fromthe group consisting of selenium and tellurium, and casting the thus-treated molten steel whereby sound cast steels characterized by improved ductility are produced.-

2. A method of producing ductile cast steels free from porosity which comprises establishing a molten mass of steel containing detrimental amounts of sulfur, treating said molten mass with a small but effective amount to about 0.6%

,of an alkaline earth metal intensifying agent and a small but effective amount to about 0.6% of at least one sulfur-desensitizing agent from the group consisting of selenium and tellurium, and casting the thus-treated molten steel whereby sound caststeels are produced which are characterized by improved ductility.

3. A method of .producing dustile cast steels free from porosity which comprises treating a molten mass of sulfur-containing steel with about 0.03% to 0.6% of calcium and about 0.01% to 0.6% of at least one sulfur-desensitizing agent from 0.02% m 0.09% sulfur, treating mid molten mm with about 0.02% to 0.08% of at least one sulfurdesensitizing agent from the group consisting of selenium and teliurium and with about 0.06% to 0.15% of calcium in the form of a calciumsilicon alloy, and casting the thus-treated molten steel whereby fine-grained steel castings are produced characterized by freedom from porosity combined with improved ductility.

6. A method of decreasing the deleterious eflect of sulfur upon the ductility of cast steels which comprises establishing a molten mass of steel containing at least 0.015% sulfur, deoxidinng said molten mass with a strong deoxidizer, treating said molten mass with about 0.01% to 0.6% or at least one sullur-desensitizing agent from the group consisting of selenium and tellurium and with about 0.03% to 0.6% of calcium, and

' casting the thus-treated molten steel whereby cast steels are produced characterized by improved ductility over similar steels not treated with said sulfur-desensitizing agent and calcium.

7. A method of producing ductile steel castings which comprises establishing a molten mass of sulfur-containing steel; treatingsald molten mass with about 0.01% to 0.25% of aluminum, about 0.01% tov 0.6% of at least one sulfurdesensitizing agent from the group consisting of selenium and tellurium, and about 0.03% to 0.0% of calcium; and casting the thus-treated molten mass whereby steel castingk are produced characterized by freedom from porosity combined with improved ductility.

8. A method of producing ductile steel castings which comprises establishing a molten mass of steel containing about 0.02% to 0.00% sulfur and about 0.1 to 0.6% carbon; treating said molten mass with about 0.01% to 0.00% aluthe group consisting of selenium and tellurium,

and casting the thus-treated molten steel whereby cast steels are produced characterized by freedom from porosity combined with improved ductllity.

4. A method of producing globular, randomly distributed sulfides in sound 'steel castings which comprises treating a molten mass of steel con- 0.015% to 0.15% sulfur and a small but effective amount up to about 9% of strengthening elements with 'about- 0.03% to 0.6% of calcium and about 0.01% to 0.6% of atleast one sulfur-desensitizing agent from the group consisting .of selenium and tellurium and casting the thus-treated molten steel whereby sound steel minum, about 0.02% to 0.08% of at least one sulfur-desensitizing agent from the group consisting of selenium and tellurium and about 0.05% to 0.15% calcium; and casting the thustreated molten mass-whereby steel castings are produced characterized by freedom from'chainlike sulfides, by fine grain size and by a higher combination of strength and ductility. including impact strength, than a similar steelnot treated with said sulfur-desensitizing agentand calcium. 9. As an article of manufacture, a cast steel characterized by a mlcrostructure containing globular, randomly distributed sulfide inclusions and containing small but detrimental amounts up to about 0.15% sulfur, small but effective amounts up to about 1.7 carbon, a small amount up to about 9% of at least one alloying element, about 0.004% to 0.5% of at least one sulfur-desensitizing agent from the group consisting of selenium and tellurium, at least about 0.002% and not exceeding the amount'resulting from adding about 0.6% of alkaline earth metal, and the balance substantially all iron.

10. As an article of manufacture, a cast steel containing sulfur up to about 0.15%. small but effective amounts up to about-1.7% carbon, about 0.004% to 0.5% of at least one sulfur desensitizing agent from the group consisting of selecastings are produced characterized byglobular randomly distributed sulfides.

5. A method of producing ductile steel castings free from porosity which lishing a molten mass of steel containing about comprises estab' lurium. about 0.002% to 0.016% of calcium, from a small but -eilective amount to about of and alloying elements, and the balance substantially all iron. r

12. As an article of manufacture, a steel casting containing about 0.02% to 0.05% sulfur. b ut 0.05% to 0.75% carbon, about 0.01% to 0.06% of at least one sulfur-desensitizing agent from the group consisting of selenium and tellurium. about 0.005% of calcium, up to about 9% of alloying and strengthening elements, and the balance substantially all iron. said steel casting being characterized by a microstructure containing globular, randomly distributed sulfide inclusions and line grains predominantly about No. 6 to 7 average grain size. v

18. As an article of manufacture, a steel casting containing about 0.015% to 0.15% sulfur, about 0.05% to 1.7% carbon, about 0.003% to 0.2% aluminum, about 0.004% to 0.5% of at least one miIur-desensitizing' agent from the group consisting of selenium and tellurium, at least about 0.002% calcium and not exceeding the amount from the group consisting of selenium and teling about calcium'iiuoride, about 10 of material from the group consisting of iron and nickel powders, and the balance calcium s'ilicide and at least one sulfur-desensitizing agent from the group consisting of selenium and tellurium, said suliur-desensitizing agent and calcium silicide being present in the proportion of about 3 parts of sulfur-desensitizing agent to about 5 parts of calcium, said addition compound being 0.03% of at least one of said sulfur-desensitizins resulting from adding about 0.8% of calcium, a.

small but effective amount up to about 9% of strengthening and alloying elements, and the balance substantially all iron.

14. As an article of manufacture, a steel casting containing about 0.015% to 0.15% sulfur, about 0.05% to 1.7% carbon, about 0.008% to 0.2% aluminum, about 0.004% to 0.5% of at least one sulfur-desensitizing agent from thegroup consisting of selenium and tellurium. about 0.002% to 0.010% calcium, and the balance substantiallvalliromsaidsteelcasting improved ductility combined with freedom from vomalwv I 15. As an article of manufacture, a steel casting containing about 0.02% to 0.05% sulfur, about 0.1% to 0.6% carbon, up to about 9% of alloying elements, about 0.003% to 0.00% aluminum, about 0.01% to 0.05% of at least one sulfur-desenaitizing agent from the group consisting of selenium and teilurium, about 0.003% to 0.005% calcium, and the balance substantially all iron, said casting being substantially free from chain-like sulilde inclusions and possessing a higher combination of strength and ductility, including impact strength, than a similar steel fies from said sulfur-desensitizing agent and calc um.

16. A method of producing ductile cast steels which comprises establishing a molten mass of steel containing sulfur, treating said molten mass with an addition compound comprising about 5% to 50% of at least one powdered fluoride reaction-accelerating agent, about 10% to 50% of material from the. group'consisting of iron and nickel powders, and the balance. at least about 10%, substantially all powder containing alkaline earth-metal and at least one sulfur-desensitizing agent from the group consisting of selenium and tellurium. said addition compound being added in'amounts suiflcient to treat the molten mass of steel with about 0.03% to 0.6% of alkaline earth metal and about 0.01% to 0.06% of "at least one of said sulfur-desensitizing agents. and f casting the thus-treated molten steel whereby sound steel castings are produced pos sessing improved ductility.

17. A method of producing ductile cast steel which comprises establishing a molten mass of steel containing sulfur, treating said molten mass with a compacted addition compound comprisagents, and casting the thus-treated molten steel whereby sound steel castings are produced characterised by improved ductility and fine grain size.

p 1 Asan article of manufacture, an improved addition compound characterized by improved reaction rates in molten metal which contains principally at least one powdered reaction-accelerating agent comprising a fluoride, material from the group consisting of iron and nickel powders, a powdered calcium-containing agent and at least one sulfur-desensitizing agent containing material from the group consisting of selenium and tellurium.

19. As an article of manufacture, an improved addition compound characterized by increased reaction rates in molten steel which comprises about 5% to of at least one powdered reaction-accelerating agent comprising a fluoride,

up to about 50% of material from the group consisting of iron and nickel powders, and the balance, at least about 10%, substantially all powder containing alkaline earth metal and at least one sulfur-desensitizing agent from the group consisting of selenium and tellurium.

20. An improved addition compound characterized by improved reaction rates which comprises about 5% to 30% of at least one powdered fluoride, about 10% to about 40% of material from the group consisting of iron and nickel powders, and the balance substantially all powder containing calcium and at least one sulfurdesensitizing agent from the group consisting of selenium and tellurium.

pound characterized by improved reaction rates which comprises about 5% to 50% of at least one powdered fluoride having .fluxing properties, about 10% to 50% otmaterial from the group consisting of iron and nickel powders, and the balance, at least about 10%, substantially all powder containing calcium and at least one sulfur-desensitizing agent from the group consisting of selenium and. tellurium.

22. An improved compacted addition compound characterized by improved reaction rates which comprises about 10% to 20% of calcium fluoride, about 10% to 40% of material from the group consisting of iron-and nickel powders, and the balance substantially'all powder containing calcium in the form of a calcium-silicon allow and at least one sulfur-desensitizing agent from the 24. As an article of manufacture, a cast steel characterized ,by a microstructure containing globular, randomly distributed sulfide inclusions and containing sulfur up to about 0.15%, carbon up to about 1.7%, a small amount up to about 9% oi at least one alloying element, a small but eii'ective amount up to about 0.5% 01' at *least one suliur-desensitizing agent,,'i'rom the group consisting of selenium and tellurium, a small'but eilective amount not exceeding the amount re l irom about 0.003% to about 0.2%, a small but 20 eil'ective amount up to about 0.5% oi at least one .sullur-desensitizing agent from the group consisting of selenium and tellurium, and the balance substantially all iron.

26. As an article oi! manufacture, a cast steel.

a en

containing small but detrimental amounts up to tellurium, aluminum up to about 0.2%, said cast steel being characterized. by a microstructure containing globular, randomly distributed sulfide inclusions.

v 27. Asan article of manufacture, a casting made of steel containing sulfur up to about 0.15%, a small but eilective amount up to about 1.7%

carbon, a small but eiiective amount up to about 0.5% of at least one'sultur-desensiti'zing agent from the group consisting of selenium and'telluriuxn, a small but eli'ective amount not exceeding the amount resulting from adding about 0.6% of alkaline earth metal, said casting being characterized by soundness of metal and improved ductility and by a microstructure containing globular, randomly distributed sulfide inclusions. ALBERT PAUL GAGNEBIN.

CERTIFICATE or CORRECTICN.

Patent No. 2,258,601 October 114., 19141.

' ALBERT PAUL GAGNYEBIN. f

It is hereby certified that err or appears, in the printed spepification of the abbve numbered patent requiring-'borretion as folldws: Page 5, first column, line 63, and second column-fiine 2, for "selium" read --aa ie aniwnage 10, first column, line 15, re;- "understood" read niderstand--;; a d second qdlumn, line 68,- claim 10, for "tellar ium" read --te11ur1ufn--; page 1.1, first column, line 67, clgiml, for "0.06%" read -0.6i--; and second dolpmn, line 63, claim 22, for "allow" read --alloyand thgt tha said Let-- tei'a.Patent should be read with this c'orrgction ther ein that the same may conform to the record of the case in.the Pntpht Office.

. Signed and sealed this-24th day of mu cn, A. 1 19i;2

1 i Henry Van hrsdal e, F v Acting bommiaxgioner f Paltenta. 

